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INA3221: "VPU" clarification

Nate Martin
Prodigy 10 points
Part Number: INA3221
We're using the INA3221 power-supply monitor in a few different applications, and I'm confused about something in the datasheet. Can anyone help me clarify?
My question is about the "VPU" pin. I think there's some contradictory information in the datasheet, but I could be misunderstanding something.
  • The "Typical application" drawing shows the PV pin pulled up to VPU, with no other connections in the drawing.
  • The Pin Configuration Table describes VPU as an Analog Input, but the description says "Pull-up supply voltage used to bias power valid output circuitry)
  • The abs-max table also says VPU is an analog input, with a max voltage of 26V. But the power valid (VP) pin (which is pulled up to VPU in the diagram) has max voltage of 6V.
  • Figure 20 "Power-Valid Output Structure" shows VPU connected to "VS"
  • Figure 55 "Layout Example" says to connect PV to VPU, and says to connect VPU to "bus power-supply rail"
  • The EVM schematic (INA3221EVM) shows VPU connected only through a resistor to PV, with no other connections (matching the typical application)
My questions are:
  1. Is the VPU pin a supply output, or an analog input?
  2. Should any connections be made between VPU and other supply rails on the board, or should it only be used to pull up PV?
  3. What would happen if we connected VPU to the same supply that all other digital outputs are pulled up to?
  • 0
    TI__Mastermind 26335 points
    Hello Nate,

    Thanks for your interest in our INA3221.

    1. VPU is an analog input.
    2. VPU can be connected to your bus which can be your supply (does not have to be). If your bus voltage will exceed 6V, then you should include RDiv (figure 20) to keep PV within device specifications. VPU alternatively can be pulled to other supply lines, assuming absolute maximum rating specifications are not exceeded.
    3. There should be no issue if you connect to the same supply as all of the other digital outputs.